1. Field of the Invention
The present invention relates to a traction drive fluid comprising a hydrocarbon, a process for producing the same and a bicyclo octane compound. More particularly, it is concerned with a traction drive fluid comprising hydrocarbon having good flowability at low temperatures and exhibiting high traction performance in a wide temperature range from low to high temperatures, a process for producing the same efficiently and a novel bicyclo octane compound. Further, the present invention relates to a process for improving the traction coefficient at high temperatures between at least two relatively rotatable elements in a torque transmitting relationship.
2. Description of the Related Arts
Generally, traction drive fluids are used in traction drive units (friction driving equipment utilizing rolling contact), for example, continuously variable transmission for automobiles, industrial equipment or hydraulic machines. Users have required that traction drive fluids should have a high traction coefficient and be stable with respect of heat and oxidation and their cost should be at a reasonable level, as the demands for them have been increasing.
In recent years, the attempts to construct small size and light weight traction drive units have been made for the sake of chiefly the automobile use and there have been emphasized the needs that Traction drive fluids intended for use in said units have been required to be capable of working under various different severe conditions and achieving stable and high performance, for example, a high traction coefficient, an adequate viscosity, and a high stability in heat and oxidation, in a wide temperature range from low to high temperatures, approximately -30.degree. to 140.degree. C.
So far, various different traction drive fluids have been developed and disclosed, for example in Japanese Patent Publication Nos. 338/1971, 339/1971 and 44918/1986, but it has been found that none of them satisfy above-mentioned required properties and is faulty on many points. Of these traction drive fluids, for example, the compounds having a high traction coefficient at high temperatures cause a large churning loss because of the high viscosity, thus resulting in low transmission efficiency, but also having poor capability to start traction drive units at low temperatures. The other compounds of a low viscosity and therefore high transmission efficiency have a significantly low traction coefficient at high temperatures and their viscosity decrease with increasing oil temperature too much, causing trouble with respect of lubrication in traction drive units.
The present inventors have made intensive studies with a view to finding the solution of above-mentioned technical difficulties of prior arts and developing a traction drive fluid having a low viscosity and exhibiting high performance in a wide temperature range.
As the result, it has been found that above-mentioned objects can be achieved with a traction drive fluid containing a bicyclo octane skeleton as the active substance and the present invention has been completed on the basis of the finding.